1. Field of the Invention
The present invention relates to devices for scanning the level of liquid media in a container, and in particular to such devices utilizing a pneumatic nozzle to direct a compressed air supply over the surface of the liquid.
2. Description of the Prior Art
Various methods and devices are known to those skilled in the art for measuring the level of liquid in containers which are being filled to a pre-determined level. Such conventional methods and devices fail to accurately monitor the level of liquid in very small containers such as, for example, electric components such as miniature relays which have a housing which is to be filled with casting resin. Moreover, in the particular situation of viscous material such as casting resins, it is preferable that the scanning take place in contact-free fashion in order to prevent the casting compound from hardening about the scanning device. Finally, such scanning must be able to take into consideration the presence of curved surfaces such as arise in small components of this type due to the surface tension and wetting.
Although contact-free pneumatic scanning is known for use in scanning solid bodies, previous scanning devices have been unsuitable for use in the casting of relays to ensure automatic disconnection and termination of the casting process when a desired fill level of casting resin has been supplied to the component housing. In particular, such known pneumatic scanning devices operate at a relatively high pressure so that the scanning air flow directed against the liquid surface changes the liquid surface and thereby prevents an accurate measurement. Moreover, the air flow is of such a high pressure that measurement of extremely thin liquid layers is effectively prevented.